This is my entry to spookyjam 2018.
So how do i music?
First, you'll need a note. You can get notes from noteblocks, by sneaking on them and activating them. The notes can be thrown around. If it lands near a skeleton, it will convert the skeleton from a dangerous undead beast, to a more musical friendly guy.
Once you have a musical skeleton, ir will have a default type of a conductor. To change this, right click it to open the gui, and at the top left there is a selection box to change the type. Once you change it to a musician, you will also need a conductor to lead the band. (This is planned to change). Once you have as many musicians and as you want, and a conductor, make sure they're all on the same channel (top right of the GUI) and play the music through the conductor.
Custom midi files also work, click the "Open Midi Folder" in the skeletons gui, and copy paste your midi there. In game, you should then be able to start playing it.